Electrical transformer system



F. DESSAUER.

' ELECTRICAL TRANSFORMER SYSTEM.

APPLICATION FILED JULY 23.1918.

Patented Mar. 22, 1921.

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ELECTRICAL TRANSFORMER SYSTEM.

APPLICATION FILED JULY 23,1918.

Patented Mar. 22, 1921.

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UNITED STATES PgENT OFFICE.

rninnmcn nnssausn, or FRANKFORT-ON-THE-MAIN, GERMANY ELECTRICAL TRANSFORMER SYSTEM.

Specification of Letters Patent.

Patented Mar. 22, 1921.

Application filed July 23; 1918. Serial No. 246,405.

To all whom it may concern.

Be it known that I, FRIEDRICH DESSnUER, a subject of the German Emperor, residing at Frankfort-on-the-Main, in the German Empire, have invented a new and useful Electrical Transformer System, of which the following is a specification.

My invention relates to an electrical high tension transformer system, and has for its object to provide an improved arran ment, as regards compactness, weight, e ciency and working security, for supplying electrical energy at high voltages.

In the accompanying diagrammatical drawings Figures 1, 2 and 3 show some arrangements as heretofore known, while Fig. 4 represents an arrangement according to myinvention, and in the Figs. 5, 6, 7, 8 and 9 other embodiments of my invention are illustrated. v

In an electrical high tension transformer of a given size, the electrical strain which the insulating layers are subjected to, and

'thus the danger that those layers be damaged or even pierced, depends upon the potential difference to which the insulating layers are subjected. In the transformers known heretofore, it is, as a rule, impossible to diminish this potential difference under a certain limiti. e. under one half of the voltage, as measured at the ends of the secondary (high tension) windin even this limit holds good only if the mi dle lpoint of the secondary coil is maintained on t e earth potential. In case, however, the secondary of the transformer is grounded at one of its ends, the potential difference cannot by any means he made smaller than the secondary voltage.

A few examples will make this clear. In Fig. 1, I have plotted as abscissae the number of turns of the secondary winding 8 of the high tension transformer T (Fig. 1), beginning from the middle m of the secondary, and as ordinates the potential difference, as measured between any oint of the secondary and the earth. Then, if in one case the middle m and in the other case one end (1)) of the secondary is grounded, the straight lines a b, and a 6 respectively. show with sufficient approximation the tension which exists between any two points of the secondary winding 8, a and 6 being the ends of the secondary. At a secondary tension of. s'ay, L00 kilovolts, we have, as 18 to be seen from the diagram, in the first case tained by grounding 1 (a 6,) a potential difference of 50 kilovolts between the earth or (what means practicallythe same) the primary winding w and iron core 2 on one hand and both a and b on the other hand, in the second case (a 6 a potential difference of 100 kilovolts between the earth or primary to and iron core 2 on one hand and one end (a) of the secondary on the other hand.

The same takes glace in Fig. 2, in which two transformers and T connected in series, are used instead of a single transformer. If in this case the conductor 0 by which the two secondaries a, and. 8 are omed together, is connected to ,the round, thensupposing the secondary tension between 62 and b to be 100 kilovoltsthe difference of potential between a as well as b on one hand and the primary w, (10,) and iron core 1', (i on the other hand will again amount to 50 kilovolts (see Fig. 2'). In any other sort of connection the result is still more unfavorable, the worst result is obone end of the secondary, say 6, in w ch case the full voltage of 100000 is established between the point a and the primary w, and iron core 5,. Obv1ously, no other result than in Fig. 1 is arrived at by a double transformation, as 1n Fig. 3,-z'. e. by inserting the primary winding p of the high tension transformer T in the circuit of the secondar 'r of a 1:1 transformer H. If instead of a step-up transformer would be used, the iron core 2' of T-itspotential being practically that of the earth-would possess a difference of potential against the primary p as well as against the secondary winding 8 of T. In any case however,-whatever the potential of the iron core 2' may be-not less than one half of the secondary voltage is present between 6 as well as w and at least one of the ends ofthe secondary winding .9 of T.

With the means, as heretofore known, we are, as is pointed out in the foregoing bound to deal with a minimum difference of potential (amounting to half the secondary voltage) between those arts of the transforming arrangement w ich are most exposed to the danger of being dama ed. In consequence, the insulating parts 0 the arrangement must be constructed according to that difference of potential. This drawback is so much the more serious, as the insulating parts in transformers are strained to the utmost by the high voltages which are in use at present in certain ap lications of transformers, such as in high vo tage testing apparatus or in Roent n-ray ap aratus for the treatment of iseases. oreover it is to be expected that still higher amounts of voltage will become desirable to be used in those just mentioned applications as well as in high tension work in general. A voltage of more than 100000 reuires cumbersome and expensive transformers to fulfil the necessary working conditions.

The essential progress brought about by my invention is involved in the fact that the unvariable relation between the secondary voltage and the strain of the dielectr c in transformers exists no longer. The manmum of potential difference between the secondary and other parts of a transformer is no lon er limited to at least the half of the secon ary voltage; it may be diminished at will. Correspondingly the difference of potential between the secondary and any part of the transformer is dlminlshed.

For the sake of more briefly expressing myself, I shall, in the following, denote as a primary winding that one of two coiiperating hi h tension transformer windings which s ows the smaller voltage at its ends, whatever the direction of energy transmission in the high tension transformer (step u or step down transformation) may be. 'Ihen according to my invention, the primary coil or coils of one or more high tension transformers of. the system are linked to the external (outside the high tension transformer) portion of the path of energy transmission by means of devices which permit the transmission of alternating current energy without the aid of a conductive relation between their energy transmitting parts, such as by transformers or condensers.

n this way I obtain the posslbility of controlling at will the potential of that portion of the path of energy transmission to which the energy is transmitted by the said devices.

Furthermore, I' maintain the primary coil, iron core and other conducting parts of each of the respective transformers at a otential which is the mean of the potential in the respective conductor, less different from the otential of the adjacent turns of the secon ary coil than this latter potential difi'eis from the potential of the ground.

I will now describe in detail, by way of example, anumber of embodimtntsof my inventions Fig-,4;- shows two transformers T, and T thesecondary coils a, and s ofr di hich are connected in series, the ratio of transformation in each transformer being that which the system as a whole is intended to possess. The primary windings p, and p, of T, and T form part each of the secondary circuit of another transformer H, and H respectivel The ratio of transformation of H, and 2 need not necessarily diifer from 1 :1; H and H are only to separate the rimsries of the high tension transformers and T from each other and from the source of current at. The point of junction 0 of the secondaries -8 and s, of T and T is grounded; therefore, at a secondary voltage of 100000 between the terminals a and b, as in the case illustrated in the diagram Fig. 4, the potential difference between either a or b on one hand and the earth on the other hand is reduced to 50 kilovolts. In consequence 25 kilovolts are established between the ground and the middle d (and e) of any of the two secondary windings s, and s,; the points at and e are connected to the primary winding p, and p, as well as to the iron cores a, and i, of T and T respec' tively. Thence, the difl'erence of potential between the end a of the secondary coil and the primary winding and iron core of T,'i. e. the maximum potential difference occurring in T,is 5025=25 kilovolts. Thus the maximum of the difference of potential between any two adjacent groups of conductors in the system is limited to one quarter of the secondary voltage; correspondingly, the electrical strain is a quarter of what it otherwise would amount to. The transformers H and H are, it is true, also bound to sustain 25 kilovolts between their primary and secondary windin s, but this requirement is easy to be fu filled, both 10 0 windings possessing equal and small numbers of turns.

As the secondary windings s, and 8 are connected in series, it is obvious that a single secondary winding may be used instead of 105 s, and 8 Therefore, the essential feature of my s stem, as shown in Fig. 4 (as well as those 0 Figs. .5, 6, I and 8), is constituted by the fact that at least three high tension transformer windin the single secondary 110 winding, as just po nted out, and the primary windings p, and p are used. and that at least two of them-p and p, -are placed each in a branch--H T and H., T, respectively-of the path of energy trans- 1 mission, every branc including (in addi tion to the high tension transformers) one or more of the devices which permit of the transmission of energy without conductive relat1on---I-I and H respectively.

Both for the fact that my transformer system is somewhat less simple than the ther transformers, as in I' of the given apparatus as before.

reduced to much less than a half, the costs of the transformers H, and H being therefore more than balanced; and this will be the more appreciable, the higher the voltages are which are to be dealt with. Moreover, the working securit is greatly increased in my system, an I wholly avoid any loss of energy by the phenomenon of silent or glow discharge (sputtering), Well known in high tension work, which loss otherwise attains considerable amounts.

Fig. 5 illustrates another form of my system, comprising three high tension transformers T T and T, having their secondaries connected in series, and only two further transformers H and H The levels of potential of the roups of conductors-supposing the midd e c of the secondary winding a, to be grounded and 140 kilovolts to be produced between the points a and bare indicated in the diagram Fig. 5 as well as in Fig. 5.

In some cases, especially with a very high voltage, I make use of more than a double transmission (as in Figs. 4 and 5), for instance of a threefold transformation, as illustrated in Fig. 6, thereby dividing the difference of potential between the high tension, circuit and the source of current (or translating apparatus) into three or more steps. In this case, by branching the path of energy transmission in some of the furi 6 (transformers G and G I preferabIy arrange these transformers so as to supply energy to more than one transformer for instance to two other transformers (I-l,, T and T,, H, respectively), in this way reducing the number of transformers required. Sup osing the middle c'of the secondary win ing .9 to be grounded and 210 kilovolts to be present between the points a and b, I have in Fig. 6 again indicated the potentials of the diverse groups of conductors.

Obviously, any one of the arrangements of Figs. 4, 5 and 6 can easily be formed out of its precedents (e. g. Fig. 6 out of Fig. 5, 4 or 1), merely by adding transformers. This is an important advantage of my systemviz., I am enabled, by my system, to adapt, by the mere addition of transformers, a given alternating current supply apparatus to a higher range of voltage, and nevertheless to make use of all the parts Preferably, I avail myself of standardized types of additional transformers (es ecially in the form of 1:1 transformers), t eir manufacture and repair being greatly simplified.

As is demonstrated by Fig. 7, I may modif my system, so as to allow the potentia of any of the several groups of conductors to be regulated at will. 11 Fig. 7, the middle d (c) of the secondary winding 8, (8,) of every one of the two high tension transformers T and T is connected to the ground by a series of condensers f, and another connection is made between the circuit of the respective primary winding 7), (p and a point It in the set of condensers. According as I choose that point of connection it, I obtain, within the limits of the potential of the middle of the secondary winding on one hand, and the ground on the other hand, any desired amount of potential in,the primary winding p, 2,) and iron core 5, (21,). Instead of a battery of condensers, as'in Fig. 7 I may make use of an adjustable resistance to bring about the adjustment of potential. In some cases I find it advisable to impart from a separate source of electrical energy the desired amount of potential to the diverse groups of conductors, instead of deriving their electrical charge from the high tension transformer or transformers.

As already mentioned, not only transformers but any device capable of transmitting electrical energy without a conductive relation between its energy transmitting parts, as, for instance, condensers, may be used to produce the separation of the groups of conductors and therefore to enable their level of potential of being adjusted. This form of my system is exemplified by Fig. 8. Fig. 8 is in accordance with Fig. 4 except that the place of the transformers H and H of Fig. 4 is taken by condensers 7c.

The artificial adjustment of the potential of the groups of conductors, according to m invention, may be advanta eously applled even to such cases in whic the maximum difference of potential between the seconda winding and the other parts of one and t e same transformer needs not be reduced to less than one half of the secondary volta e. Inthe case, say, of a high tension trans ormer with one end of its secondary winding grounded by any reason, the maximum difference of potential acting upon the insulating layers in the arrangement, as known heretofore, amounts-as is stated aboveto the total of secondary voltage of the transformer, and cannot be reduced by any means. By inserting an intermediate circuit, the level of potential of which is made adjustable, according. to my invention, I reduce the strain of the insulatmg layers to one half of what is unavoidably amounted tocet. pain-in the heretofore known transformers with one end of the seconda winding grounded. This is demonstrate by Fig. 9 which shows an arrangement similar to that of Fig. 3. As already stated in connection with Fig. 3, it is impossible to reduce the strain of the insulatmg layers by a mere repeated transformation. If, however, the intermediate circuit Z and iron core '11 is, as in Fig. 9, connected to the middle 0 of the secondary (high tension) winding 3, or otherwise kept on a level of potential situated between the potentials of the ends a, and b of s on one hand and of pared with the surrounding coils.

What I claim is: v

1. In a high tension transformer system, a high tension transformer, devices for linking the primary coil thereof with the source of alternating current, said devices having alternating energy transmitting parts in nonconductive relation, and means for maintaining a less difference of potential between the iron core and primary coils, on the one hand, and the adjacent turns of the secondary, on the other, than that existing between the latter and ground.

2. A high tension system comprising one or more hi h tension transformers, one or more transfhrmers linking the primary coils of said high tension transformers with a source of alternating current, said high tension transformers having conductive couplings between each primary coil, core, and coil of high tension circuit thereof at a point in said circuit between which and the round the maximum difference of potential s equal to or greater than the maximum potential difference between any turn of said high tension circuit and the primary coil coupled therewith.

3. A high tension system comprising one or more high tension transformers, one or more transformers having an approximate one to one ratio of transformation for linking the primary coils of-said high tension transformers with a source of alternating current, said high tension transformers having conductive couplings between each primary coil, core, and coils of high tensionv circuit thereof at a point in said circuit between which and the ground the maximum difference of potential is equal to or greater than the maximum potential difference between any turn of said high tension circuit and the primary coil coupled therewith.

4. A high tension system comprising one or more hi h tension transformers, one or more trans ormers linking the primary coils of said high tension transformers with a source of alternating current, said high tension transformers having couplings between such primar coil, core, and coils of hi h tension circuit thereof at a point in said circuit between which and the ground the maximum difference of potential is equal to or greater than the maximum potential difference between any turn of said high tension circuit and the primary coil coupled therewith.

5. In a high tension transformer system, three or more high tension transformer windings, two or more branches of energy transmission, each branch including one of said windings and one or more transformers, the primary coils of the transformers being coupled with a point of the high tension circuit between which and the turns of the secondary coil adjacent to the corresponding primary there is a difference of potential equal to or less than the maximum potential difference between said secondary coil and the ground.

6. In a high tension transformer system, three or more high tension transformer windings, two or more branches of energy transmission, each branch including one of said windings and one or more transformers, the primar coils of the transformers being couple with a point of the high tension circuit between which and the turns of the secondary coil adjacent to the corresponding primary there is a difference of potential equal to or less than the maximum potential difference between said secondary coil and the ground, the said intermediate transform ers having an approximate one to one ratio of transformation.

7. In a high tension transformer system, a high tension transformer, devices for linking the primary coil thereof with alternating current energy, said devices having altcrnating energy transmitting parts in nonconductive relation, and means for maintaining a less difference of potential between conductive parts of the transformer adjacent to each other than that existing between high tension turns thereof and the ground.

8. In a high tension transformer system, one or more high tension transformers, a plurality of transformers linking the primary coils of said high tension transformers with the external portion of the path of energy transmission, said primary coils and iron cores of the respective transformers having conductive couplings between each. primary coil and coil of high tension circuit thereof at a point in said circuit between which and the ground the maximum difference of potential is equal to or greater than the maximum potential difference between any turn of said high tension circuit and the primary coil coupled therewith, three or more steps of potential thereby being formed in the system, and the path of energy transmission being branched on one or more of the intermediate levels of potential produced by said steps of potential.

9. In a high tension transformer system. one or more high tension transformers, a

plurality of transformers having an approximate one to one ratio of transformation for linking the primary coils of said high tension transformers with the external portion of the path of energy transmission, said primary coils and iron cores of the respective transformers having conductive couplings between each primary coil and coil of high tension circuit thereof at a point in said circuit between which and the ground the maximum difference of potential is equal to or greater than the maximum potential difference between any turn of said high tension circuit and the primary coil coupled therewith, three or more steps of potential thereby being formed in the system, and the path of energy transmission being branched on one or more of the intermediate levels of potential produced by said steps of potential.

10. A high tension system comprising a plurality of primary and secondary transformer windings having the secondary windings of high potential circuits connected in series, a source of alternating electrical energy, and means.for supplying the primary transformer windings with energy derived from said source and insulating said source therefrom whereby a potential difference may be maintained between said primary windings different from the potential of the source.

11. A high tension system comprising a plurality of prima and secondary transformer windings lhaving the secondary windings of high potential circuits connected in series, a source of alternating electrical energy, and means comprising separate transformers of preferably a one to one ratio of transformation as compared with the ratio of the high tension transformer windings for supplying the primary transformer windings with energy and insulating said source therefrom whereby a potential difference may be maintained between said primary windings difi'erent from the potential of the source.

12. A hi h tension system comprising a plurality 0% primary and secondary transformer windings having the secondary windings of high potential circuits connected in series, a source of alternating electrical energy, means for supplying the primary transformer windings with energy derived from said source, and couplings between the said primary windings and their corresponding secondary high tension windings at suitable points in the high tension circuit.

13. A high tension system comprising a plurality of primary and secondary transformer windings having the secondary windings of high potential circuits connected in series, a source of alternating electrical energy, means for supplying the primary transformer windings with energy derived from said source, and means for keeping said primary windings at a desired potential with respect to said high tension windlugs.

14. In a high tension system, a transformer having its primary and secondary conductively coupled at a point between which and the ground the maximum difference of potential is equal to or greater than the maximum otential difference between any turn of t e high tension circuit and the primary coupled therewith, a source of alternating current for supplying said primary winding with energy, and means for keeping said transformer insulated from said source.

MARTIN HUBNER, GUSTAV SPIER. 

